Pawnee Montane Skipper Recovery Plan
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Pawnee Montane Skipper Butterfly Recovery Plan Prepared by: September 1998 PAWNEE MONTANE SKIPPER RECOVERY PLAN Prepared by the Pawnee Montane Skipper Recovery Working Group for Region 6 U.S. Fish and Wildlife Service Denver, Colorado Bettina Proctor Terry Ireland U.S. Fish and Wildlife Service U.S. Fish and Wildlife Service, Region 6 Region 6 Denver, Colorado Grand Junction, Colorado Scott Ellis Janet Coles ENSR Colorado Natural Areas Program Fort Collins, Colorado Denver, Colorado Denny Bohon Frank Kunze U.S. Forest Service Jefferson County Open Space South Platte Ranger District Golden, Colorado Morrison, Colorado Paul Opler Bob Taylor Biological Resources Division Denver Water Department U.S. Geological Survey Denver, Colorado Fort Collins, Colorado Don Kennedy Denver Water Department Denver, Colorado ________ // 7 / /. .‘ / Approved: ~ Ct’ • Y-~-t~; ~‘7 Regional Director, Region 6, U.S. Fish and Wildlife Service /72,7 7 Date: / — / / ACKNOWLEDGMENT This Recovery Plan is dedicated to working group member, Bob Taylor, Denver Water Department, who passed away as the Plan was being finished. We are grateful to Bob for his interest in and concern for the Pawnee montane skipper and his energy and unflagging sense of humor which helped guide us. DISCLAIMER Recovery plans delineate reasonable actions which are believed to be required to recover and/or protect listed species. Plans are prepared by the U.S. Fish and Wildlife Service and are sometimes prepared with the assistance of recovery teams, contractors, State agencies, and others. Objectives will be attained and funds expended contingent upon appropriations, priorities, and other budgetary constraints. Recovery plans do not necessarily represent the views or the official positions or approval of any individuals or agencies, other than the U.S. Fish and Wildlife Service, involved in the plan formulation. They represent the official position of the U.S. Fish and Wildlife Service .~nly after they have been signed by the Regional Director or Director as ~ Approved recovery plans are subject to modification as dictated by new findings, changes in species status, and the completion of recovery tasks. i Literature Citations should read as follows: U.S. Fish and Wildlife Service. 1998. Pawnee montane skipper butterfly J~ksp~ri~ leonardus montana) recovery plan. Denver, Colorado. 16 pages. Additional copies may be purchased from: The Fish and Wildlife Service Reference Service 5430 Grosvenor Lane, Suite 110 Bethesda, Maryland 20814 telephone: 301/429-6403 or 1-800-582-3421 fax: 301/564-4059 e-mail: [email protected] Fees for plans vary depending on the number of pages. ii EXECUTIVE SUMMARY £urr~nLSt~tu~: The Pawnee montane skipper (1ksp~ri~ I n~rdu~ in~n1an~) is listed as threatened. The only known population occurs on the Pikes Peak Granite Formation in the South Platte River drainage system in Colorado. Estimated total known habitat is 37.9 square miles and is owned and/or administered by the Denver Water Department, the U.S. Forest Service (Pike National Forest), Jefferson County, and private individuals. Habitat Requirements and Limiting Factors: Pawnee montane skippers inhabit dry, open Ponderosa pine woodlands with sparse understory at 6,000 to 7,500 feet with moderately steep lopes and with soils derived from Pikes Peak granite. Blue grama grass, the larval food plant, and prairie gayfeather, the primary nectar plant, are two necessary components of the ground cover. Recovery Objective: Delisting R~yexy~riI~ua. 1. Protect and maintain through proper vegetation management, all of the defined skipper habitat on public land in the South Platte River drainage. 2. Avoid habitat fragmentation. 3. Ensure that skippers are distributed throughout the range. ~ 1. Create Memoranda of Understanding among land management agencies to provide for maintenance and enhancement of habitat. 2. Monitor skipper presence in habitat. 3. Monitor skipper habitat quality and trends. 4. Determine management criteria for habitat maintenance. 5. Educate private landowners and seek opportunities for conservation agreements to allow enhancement of skipper habitat on private lands. Total Cost of Recovery: $330,000 ~f~y~y: 2010 iii TABLE OF CONTENTS PART I. INTRODUCTION Description Distribution Habitat’Ecosystem Population Status Reasons for Listing Conservation Measures PART II. RECOVERY Objective Criteria for Delisting Step-down Outline Narrative Literature Cited PART III. IMPLEMENTATION SCHEDULE PART IV. SUMMARY OF PUBLIC COMMENTS PART I - INTRODUCTION D~pfl~n The Pawnee montane skipper is a member of the skipper butterfly family (Hesperiidae) and was first described in 1911 as Pamphila montan~j (Skinner 1911). Scott and Stanford (1982) combined two species (Hesnei~iapa~’n~ and Hesperia leonardus), retained the specific name k~nardu~, and treated the Pawnee montane skipper as Hesperia leonardus montan~’. It was officially listed as Hesperia leonardus montana in the iE~ ra1R~gi~r as a threatened species on September 25, 1987 (52 FR 36176). The Pawnee montane skipper is a small brownish-yellow butterfly with a wing span slightly over 1 inch. Small, fulvous (dull brownish-yellow), usually distinct spots occur near the outer margins of the upper surface of the wings, while one to four distinct brownish to off-white spots occur on the lower (ventral) surface of the wings. The ventral spots are larger on the hind wing and generally are whiter in the female butterflies. Di~tributiQn The Pawnee montane skipper (skipper) occurs only on the Pikes Peak Granite Formation in the South Platte River drainage system in Colorado, involving portions of Jefferson, Douglas, Teller, and Park Counties. Two other subspecies are in this group, including Iksp~rj~ leonardus leonardus in the eastern United States and Canada, and Hesperia leonardus pawnee in the Northern Great Plains. The presence of ventral hind wing spots and its darker color differentiates Hesperia leonardus montana from Hesperia leonardus pawnee (Scott and Stanford 1982). An intensive distribution survey was conducted within the South Platte drainage by the consulting firms of Environmental Research & Technology, Inc. (ERT) and Professional Entomological Services Technology, Inc. (PEST) during August and September 1985. They found the range of the skipper to be centered at Deckers, Colorado, and to extend northwestward just beyond Pine, Colorado, and southward to the point where the county lines of Teller, Park, Jefferson, and Douglas Counties nearly converge. This total area is roughly 23 miles long and 5 miles wide. The total known habitat within this range is estimated to be 37.9 square miles. The area occupied by the skipper is owned and/or administered by the U.S. Forest Service (Pike National Forest), Jefferson County, Colorado State Land Board, and the Bureau of Land Management. Denver Water Department and private individuals own the rest of the habitat. 1 Ha~E~Qsy~m The skippers occur in dry, open, Ponderosa pine ~IPinui.p=~nd~r~)woodlands at an elevational range of 6,000 to 7,500 feet. The slopes are moderately steep with soils derived from Pikes Peak granite. The understory is limited in the pine woodlands. Blue grama grass (Bouteloua gracilis), the larval food plant, and the prairie gayfeather (Liatrii.pi.in~iat~), the primary nectar plant, are two necessary components of the ground cover strata. Small clumps of blue grama occur throughout the warm, open slopes inhabited by skippers. Prairie gayfeather occurs throughout the ponderosa pine woodlands. Skippers are very uncommon in pine woodlands with a tall shrub understory (Keenan et al. 1986) or where young conifers dominate the understory (ERT 1986). Based on quantitative skipper occurrence studies (ERT 1986), general characteristics of Pawnee montane skipper habitat include: • Tree canopy cover of 30 percent. • Ponderosa pine crown cover of 25 percent, Douglas fir crown cover of 5 percent. • Tree density of less than 120 trees/acre in the smallest size class (0 to 5 feet diameter breast high); overall tree density of less than 200/acre. • Shrub and grass cover generally less than 10 percent. • Prairie gayfeather flower stem density ranging from 50 to 500/acre. • Blue grama cover 5 percent or less, present nearly everywhere. The vegetative community preferred by the skipper is a northern-most extension of the ponderosa pine/blue grama grass habitat type documented from southern Colorado and northern New Mexico. However, the preferred nectar plant of the skipper, prairie gayfeather, does not occur in similar habitats to the south. The northeastern limit of the ponderosa pine/blue grama grass community overlapping with the southwestern limit of the prairie gayfeather may contribute to the maintenance of the species in this limited area. Its existence in this limited and specialized area accentuates the ecological precariousness of the skipper. Life history/Ecology Pawnee montane skippers emerge from their pupae as adult butterflies in late July. Usually males emerge before females by an average of 7 to 10 days. Adults spend most of their short existence feeding and mating. Adult females deposit eggs singly and directly on leaves of blue grama grass, which is the larval food plant (Scott and Stanford 1982, McGuire 1982, Opler 1986). The species overwinters as young larvae, and little is known of the larval and pupal stages. Pupation is generally short (13-23 days) in most butterfly species. The skipper 2 completes its life cycle (egg to larva to pupa to adult butterfly to egg) annually (Keenan et al. 1986). ERT (1986) indicated that adult skippers probably fly until a major killing frost occurs. They also stated that the skippers emerge when the prairie gayfeather flowers. During 1986, the prairie gayfeather began blooming in late July, which coincided with the first observation of adult Pawnee montane skippers. The prairie gayfeather was still being used as the preferred nectar source when the last Pawnee montane skipper observations were made on September 17, 1986. The prairie gayfeather apparently requires openings from single event disturbance such as logging or fire-created habitat but does not tolerate continuous disturbance.